1. Field of the Invention
The present invention relates to a vertical filter circuit for a picture in picture display device of a television system and more particularly to a circuit capable of vertically filtering image data to be received in accordance with a scan mode. A method for vertical filtering is also disclosed.
The instant application is based on Korean Patent Application No. 94-18113 (1994) which is incorporated herein by reference for all purposes.
2. Brief Discussion of Related Art
In many late model television sets, a picture in picture display (hereinafter, simply PIP) can simultaneously display both a main picture and a compressed image. In this case, the PIP display is embodied by a PIP exclusive-use integrated circuit, in which a vertical filter is used for compressing image data of a horizontal line.
Furthermore, when a television set achieves a certain, i.e., large, size, the picture may be rough and unpleasant to a user's eye due to enlargement of the scanning interval of the picture. To prevent this problem, a double scan method, in which the number of scanning lines is doubled, is generally applied to large-sized television sets. In this case, since the large-sized television set having a double scan mode is different from a television set having a normal scan mode in the number of scanning lines, a separate PIP exclusive-use integrated circuit has to be used therein.